The present invention relates to a process for preparing a 1,5-diaminonaphthalene derivative. In particular, it relates to a process for preparing a 1,5-diaminonaphthalene derivative using a 5-nitro-1-tetralone derivative as starting material. A 1,5-diaminonaphthalene derivative prepared according to the process of this invention is useful as a material for a variety of synthetic resins. For example, a 1,5-diaminonaphthalene derivative may be reacted with phosgene to form a diisocyanate, which may be then converted into a polyurethane resin, a dicarboxylic acid or its derivative to provide a polyamide resin.
Conventionally, a 1,5-diaminonaphthalene derivative has been prepared by nitrating naphthalene to produce a dinitronaphthalene and then reducing the nitro groups into amino groups. Dinitration of naphthalene, however, produces a 1,8-dinitro derivative in a large amount in addition to the desired 1,5-dinitro derivative. For example, in nitration of 1-nitronaphthalene in a chlorine-containing organic solvent as described in Japanese Laid-open Patent Publication No. 51-070757, 1,5-dinitronaphthalene is produced in an yield of 30% while 1,8-dinitronaphthalene in an yield of 65%. That is, the 1,8-dinitro derivative is formed in a two-fold or more amount of the 1,5-dinitro derivative. 1,8-Dinitronaphthalene may be readily reduced into 1,8-diaminonaphthalene, which may be, for example, used as a material for a dye. However, when a demand for 1,8-diaminonaphthalene is reduced, production of 1,5-dinitronaphthalene is reduced, making 1,5-diaminonaphthalene less available.
In the light of such status, there have been attempts for increasing an yield of the 1,5-derivative in nitration of naphthalene. For example, WO 99-12887 has described that using Nafion(copyright) as an acid, 1-nitronaphthalene is nitrated with nitric acid to give 1,5- and 1,8-dinitronaphthalenes in yields of 34.1% and 38.0%, respectively. Thus, the proportion of the 1,5-dinitro derivative may be improved, but the 1,8-derivative is still formed in a large amount.
As described above, the current preparation procedure produces the 1,8-dinitro derivative in a large amount in addition to the 1,5-dinitro derivative. Thus, there has been needed to provide a process for selectively producing a 1,5-diaminonaphthalene derivative without forming isomers.
Besides the process involving dinitration of naphthalene and reduction of the nitro groups, many alternative processes have been suggested; for example, amination of 1,5-dihydroxynaphthalene as a starting material (U.S. Pat. No. 5,113,025, Japanese Laid-open Patent Publication No. 59-29061), amination of a 5-halogeno-1-aminonaphthalene or 1,5-dihalogenonaphthalene (Japanese Laid-open Patent Publication No. 7-278066, U.S. Pat. No. 3,787,496) and amination of sodium 1,5-naphthalenedisulfonate (Nihon Kagakukai Shi, 522 (1974)). However, a cumene process for preparing 1,5-dihydroxynaphthalene tends to cause rearrangement of a isopropyl group in 1,5-diisopropylnaphthalene as a starting material to the xcex2-position due to steric hindrance, leading to formation of isomers as is in the process involving dinitration and reduction. It is, therefore, not a selective method. Halogenation or sulfonation of naphthalene is also less selective.
We have intensely investigated for providing a process for selectively preparing a 1,5-diaminonaphthalene derivative without forming isomers, and have found a process for preparing a 1,5-diaminonaphthalene derivative using a 5-nitro-1-tetralone derivative as an intermediate, achieving this invention.
Specifically, this invention comprises the embodiments described in the following [1] to [7].
[1] A process for preparing a 1,5-diaminonaphthalene derivative comprising:
(i) the first step comprising reacting an ortho-alkylnitrobenzene represented by formula (1): 
wherein R1 to R4, which may be the same or different, represent hydrogen, alkyl having 1 to 4 carbon atoms, aromatic hydrocarbon having 6 to 12 carbon atoms, or halogen; and R5 represents hydrogen, with a vinyl compound represented by formula (2): 
wherein R6 and R7, which may be the same or different, represent hydrogen, alkyl having 1 to 4 carbon atoms, or halogen; and X represents an electron withdrawing group, provided that R6 and R7 are mutually cis- or trans-configured, in the presence of a base, to produce an aromatic nitro compound represented by formula (3): 
wherein R1 to R7 are as defined in formulas (1) and (2); and X represents an electron withdrawing group, which may be the same as or different from X as defined in formula (2);
(ii) the second step of cyclizing the aromatic nitro compound represented by formula (3) to produce a 5-nitro-1-tetralone derivative represented by formula (4): 
wherein R1 to R4 and R6 to R7 are as defined in formulas (1) and (2); and
(iii) the third step comprising reacting the 5-nitro-1-tetralone derivative represented by formula (4) with an amine to provide an intermediate, which is then reduced and aromatized to produce the 1,5-diaminonaphthalene derivative represented by formula (5): 
wherein R1 to R4 and R6 to R7 are as defined in formulas (1) and (2).
[2] The process as described in [1], wherein X in formula (2) is one selected from the group consisting of CN and CO2R8 where R8 represents alkyl having 1 to 7 carbon atoms, cycloalkyl, aromatic hydrocarbon having 6 to 12 carbon atoms or aralkyl.
[3] The process as described in [1], wherein X in formula (3) is one selected from the group consisting of CONH2, CN, CO2H and CO2R8 where R8 represents alkyl having 1 to 7 carbon atoms, cycloalkyl, aromatic hydrocarbon having 6 to 12 carbon atoms or aralkyl.
[4] The process as described in [1] or [2], wherein the reaction of the ortho-alkylnitrobenzene represented by formula (1) with the vinyl compound represented by formula (2) in the first step is conducted in the presence of at least one selected from the group consisting of a solvent capable of dissolving at least part of the base and a catalyst capable of solubilizing the base.
[5] The process as described in [4], wherein the solvent capable of dissolving at least part of the base is a circular urea derivative.
[6] The process as described in any of [1] to [5], wherein in the third step, a hydroxylamine derivative as the amine is reacted with the 5-nitro-1-tetralone derivative represented by formula (4) or an ammonia derivative as the amine is reacted with the 5-nitro-1-tetralone derivative represented by formula (4) in the presence of hydrogen peroxide, to provide an oxime represented by formula (6): 
wherein R1 to R4 and R6 to R7 are as defined in formulas (1) and (2), which is then converted by aromatization into a 5-nitro-1-aminonaphthalene derivative represented by formula (7): 
wherein R1 to R4 and R6 to R7 arc as defined in formulas (1) and (2), which is then reduced into the 1,5-diaminonaphthalene derivative represented by formula (5).
[7] The process as described in any of [1] to [5], wherein in the third step, an ammonia derivative as the amine is reacted with the 5-nitro-1-tetralone derivative represented by formula (4) to provide an imine represented by formula (8): 
wherein R1 to R4 and R6 to R7 are as defined in formulas (1) and (2), which is then reduced and aromatized to provide the 1,5-diaminonaphthalene derivative represented by formula (5).
The above process wherein an ortho-alkylnitrobenzene derivative and a vinyl compound are used as starting materials to give a 5-nitro-1-tetralone derivative, from which a corresponding 1,5-diaminonaphthalene derivative is prepared, allows the 1,5-diaminonaphthalene derivative to be selectively prepared without forming isomers.
First, there will be described the first step in the process according to this invention, in which an ortho-alkylnitrobenzene derivative is reacted with a vinyl compound to prepare an aromatic nitro compound.
In the present invention, in formula (1), R1 to R4 may be the same or different, and represent hydrogen, alkyl having 1 to 4 carbon atoms, aromatic hydrocarbon having 6 to 12 carbon atoms or halogen; and R5 represents hydrogen.
In the present invention, in formula (2), R6 and R7 may be the same or different, and represent hydrogen, alkyl having 1 to 4 carbon atoms or halogen; X represents an electron withdrawing group; and R6 and R7 are mutually cis- or trans-configured.
Examples of alkyl in R1 to R4 and R6 and R7 include methyl, ethyl, n-propyl, isopropyl, n-butyl, i-butyl and t-butyl.
Examples of aromatic hydrocarbon in R1 to R4 include phenyl, tolyl and xylyl.
Examples of halogen in R1 to R4 and R6 and R7 include fluorine, chlorine, bromine and iodine.
In formula (2), R8 when X is CO2R8 represents alkyl having 1 to 7 carbon atoms, cycloalkyl, aromatic hydrocarbon having 6 to 12 carbon atoms, or aralkyl. Examples of alkyl having 1 to 7 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, i-butyl, t-butyl, n-pentyl and n-hexyl. Examples of cycloalkyl include cyclopentyl and cyclohexyl. Example of aromatic hydrocarbon include phenyl, tolyl and xylyl. Examples of aralkyl is benzyl and phenethyl.
In the present invention, examples of an ortho-alkylnitrobenzene derivative represented by formula (1) include 2-methylnitrobenzene, 2-methyl-6-isopropylnitrobenzene, 2-methyl-5-t-butylnitrobenzene, 2,4-dimethylnitrobenzene, 2-methyl-4-chloronitrobenzene, 2-ethylnitrobenzene and 2-benzylnitrobenzene.
In the present invention, examples of an electron withdrawing group X in a vinyl compound represented by formula (2) is preferably one selected from the group consisting of CN and CO2R8 where R8 represents alkyl having 1 to 7 carbon atoms, cycloalkyl, aromatic hydrocarbon having 6 to 12 carbon atoms or aralkyl. Examples of an acrylonitrile derivative in which X is CN include acrylonitrile, methacrylonitrile, crotononitrile, 2-chloroacrylonitrile, 3-chloroacrylonitrile and 3-ethylacrylonitrile. Examples of an acrylate in which X is CO2R8 include methyl acrylate, ethyl acrylate, isopropyl acrylate, t-butyl acrylate, methyl methacrylate, methyl crotonate, methyl 2-chloroacrylate, methyl 3-chloroacrylate and isopropyl 3-chloroacrylate.
Examples of a nitrobenzenenitrile derivative represented by formula (3), in which X is nitrile, include 4-(2-nitrobenzene)butanonitrile, 4-(2-nitrobenzene)-2-methylbutanonitrile, 4-(2-nitrobenzene)-3-methylbutanonitrile, 4-(2-nitrobenzene)-3-ethylbutanonitrile, 4-(2-nitrobenzene)-3-chlorobutanonitrile, 4-(2-nitrobenzene)-n-heptanonitrile, 4-(2-nitro-3-isopropylbenzene)butanonitrile, 4-(2-nitro-3-butylbenzene)butanonitrile, 4-(2-nitro-4-t-butylbenzene)butanonitrile, 4-(2-nitro-5-methylbenzene)butanonitrile and 4-(2-nitro-3-methylbenzene)-2-methylbutanonitrile. In particular, 4-(2-nitrobenzene)butanonitrile is preferable because it can be converted into a 5-nitro-1-tetralone which used in a variety of applications.
Examples of a nitrobenzenecarboxylic acid represented by formula (3) where X is carboxyl, include 4-(2-nitrobenzene)butyric acid, 4-(2-nitrobenzene)-2-methylbutyric acid, 4-(2-nitrobenzene)-3-methylbutyric acid, 4-(2-nitrobenzene)-3-ethylbutyric acid, 4-(2-nitrobenzene)-3-chlorobutyric acid, 4-(2-nitro-3-isopropylbenzene)butyric acid, 4-(2-nitro-3-butylbenzene)butyric acid, 4-(2-nitro-4-t-butylbenzene)butyric acid, 4-(2-nitro-5-methylbenzene)butyric acid, 4-(2-nitro-5-methylbenzene)butyric acid and 4-(2-nitro-3-methylbenzene)-2-methylbutyric acid. In particular, 4-(2-nitrobenzene)butyric acid is preferable because it can be converted into a 5-nitro-1-tetralone which is used in a variety of applications.
Examples of a nitrobenzenecarboxylate represented by formula (3) where X is CO2R8 include methyl 4-(2-nitrobenzene)butyrate, methyl 4-(2-nitrobenzene)-2-methylbutyrate, methyl 4-(2-nitrobenzene)-3-methylbutyrate, methyl 4-(2-nitrobenzene)-3-ethylbutyrate, methyl 4-(2-nitrobenzene)-3-chlorobutyrate, methyl 4-(2-nitro-3-isopropylbenzene) butyrate, methyl 4-(2-nitro-3-butylbenzene) butyrate, methyl 4-(2-nitro-4-t-butylbenzene) butyrate, methyl 4-(2-nitro-5-methylbenzene) butyrate, methyl 4-(2-nitro-3-methylbenzene)-2-methylbutyrate, ethyl 4-(2-nitrobenzene)butyrate, ethyl 4-(2-nitrobenzene)-2-methylbutyrate, ethyl 4-(2-nitrobenzene)-3-methylbutyrate, ethyl 4-(2-nitrobenzene)-3-ethylbutyrate, ethyl 4-(2-nitrobenzene)-3-chlorobutyrate, ethyl 4-(2-nitro-3-isopropylbenzene) butyrate, ethyl 4-(2-nitro-3-butylbenzene) butyrate, ethyl 4-(2-nitro-4-t-butylbenzene) butyrate, ethyl 4-(2-nitro-5-methylbenzene) butyrate, ethyl 4-(2-nitro-3-methylbenzene)-2-methylbutyrate, cyclohexyl 4-(2-nitrobenzene)butyrate, phenyl 4-(2-nitrobenzene)butyrate and benzyl 4-(2-nitrobenzene)butyrate. In particular, methyl and ethyl 4-(2-Nitrobenzene)butyrate are preferable because they can be readily converted into a 5-nitro-1-tetralone which is used in a variety of applications.
Examples of a nitrobenzenecarboxamide represented by formula (3) where X is CONH2, include 4-(2-nitrobenzene)butyramide, 4-(2-nitrobenzene)-2-methyl butyramide, 4-(2-nitrobenzene)-3-methylbutyramide, 4-(2-nitrobenzene)-3-ethyl butyramide, 4-(2-nitrobenzene)-3-chlorobutyramide, 4-(2-nitrobenzene)-heptyramide, 4-(2-nitro-3-isopropylbenzene)butyramide, 4-(2-nitro-3-butylbenzene)butyramide, 4-(2-nitro-4-t-butylbenzene)butyramide, 4-(2-nitro-5-methylbenzene)butyramide, 4-(2-nitro-5-methylbenzene)butyramide, 4-(2-nitro-3-methylbenzene)-2-methylbutyramide and 4-(2-nitro-5-methylbenzene)-valeramide. In particular, 4-(2-nitrobenzene)butyramide is preferable because it can be converted into a 5-nitro-1-tetralone, which is used in a variety of applications.
The compounds represented by formulas (1) to (3) are not limited to those described above.
A nitrobenenecarboxamide represented by formula (3) where X is CONH2 can be prepared by reacting a nitrobenzenenitrile derivative represented by formula (3) where X is nitrile with water under acidic conditions. An acid used for reaction of the nitrobenzenenitrile derivative with water under acidic conditions may be any acid by which the nitrile group can be protonated; for example, sulfuric acid and sulfonic acids such as p-toluenesulfonic acid, chlorosulfonic acid, trifluoromethanesulfonic acid. Sulfuric acid is preferable because it is inexpensive and readily available. The amount of the acid used must be one or more equivalent to the nitrobenzenenitrile derivative. The reaction is initiated by contacting the nitrobenzenenitrile derivative with the acid under anhydrous conditions. A contact temperature and a contact period may vary depending on the type and the amount of the acid. For example, when using 20 equivalents of sulfuric acid, the reaction can be substantially completed by treatment at 100xc2x0 C. for 4 hours. In the reaction, a solvent may be used, which must be inert during the reaction. A reaction pressure may be an ambient, increased or reduced pressure as long as a proper reaction temperature can be maintained.
Then, the mixture of the acid and the nitrobenzenenitrile derivative can be reacted with water to provide a nitrobenzenecarboxamide. The amount of water used must be one or more equivalent to the nitrobenzenenitrile derivative. A reaction temperature may vary depending on the type of the acid, but a lower temperature is generally advantageous. If the reaction is conducted at an elevated temperature, the nitrobenzenecarboxamide may be further hydrolyzed into a corresponding nitrobenzenecarboxylic acid. A reaction temperature is 50 to 200xc2x0 C., preferably 50 to 150xc2x0 C. A reaction period may be quite short; specifically, 5 min or less is sufficient. A longer reaction period may lead to hydrolysis to the nitrobenzenecarboxylic acid as is at a higher reaction temperature. As described above, a reaction temperature and a reaction period must be carefully chosen. Herein, water containing a basic compound may be used. Specifically, water containing a basic compound may be added, or alternatively a basic compound or water containing a basic compound may be added after adding water. By adding a basic compound, a higher reaction temperature and a longer reaction period may be employed while preventing hydrolysis into a nitrobenzenecarboxylic acid derivative.
A nitrobenzenecarboxamide may be obtained as crystals after reacting with water when it has a higher melting point or is highly crystallizable. The crystals may be washed with water for removing the acid, salts and/or the basic compound. If necessary, the crystals are purified by, for example, recrystallization. When a melting point is too low to give crystals after reaction with water, the product may be extracted, concentrated as usual, and then isolated by, for example, distillation or recrystallization. These treatments or reactions are preferably conducted in a liquid phase, and may be conducted batchwise or in a continuous system.
Alternatively, a nitrobenzenecarboxamide may be prepared by reacting a nitrobenzene carboxylic acid represented by formula (3) where X is carboxyl and/or its derivative (an ester or acid halide), with ammonia.
When directly reacting the nitrobenzenecarboxylic acid with ammonia, a compound which can act as a dehydrating agent or a condensing agent such as DCC may be used. In the reaction without a condensing agent, the system must be heated. The reaction may be conducted either in a liquid or a gaseous phase, but a liquid phase is preferable in the light of a volumetric efficiency. Although the reaction may be conducted without a solvent, ammonia liquefied in an autoclave may be used as a solvent or alternatively a solvent inert to the reaction may be added. A reaction temperature and a reaction period may vary depending on the type of a dehydrating agent or condensing agent used. A reaction pressure is preferably an ambient pressure or higher.
When reacting an ester of a nitrobenzenecarboxylic acid with ammonia, a catalyst may be added. Without a catalyst, the reaction system must be heated. The reaction may be conducted either in a liquid phase or in a gaseous phase, but a liquid phase is preferable in the light of a volmetric efficiency. Although the reaction may be conducted without a solvent, ammonia liquefied in an autoclave may be used as a solvent or alternatively a solvent inert to the reaction may be added. A reaction temperature and a reaction period may vary depending on the type of a catalyst used. A reaction pressure is preferably an ambient pressure or higher.
When reacting an acid halide of a nitrobenzenecarboxylic acid with ammonia, a catalyst may be added, a desalting agent may be added, or an excessive ammonia may be added as a desalting agent. The reaction may be conducted either in a liquid phase or in a gaseous phase, but a liquid phase is preferable in the light of a volmetric efficiency. Although the reaction may be conducted without a solvent, ammonia liquefied in an autoclave may be used as a solvent or alternatively a solvent inert to the reaction may be added. A reaction temperature and a reaction period may vary depending on the type of a catalyst or desalting agent used. A reaction pressure is preferably an ambient pressure or higher.
These reactions may be conducted batchwise or in a continuous system.
The reaction of the compounds represented by formulas (1) and (2) in the first step in the process according to the present invention is conducted in the presence of a base, preferably a strong base. Examples of such a strong base include solid bases such as NaOH, KOH, LiOH, Na2CO3, K2CO3, CH3ONa, t-BuOK, NaH, C6H5ONa, (CH3)4N+OHxe2x88x92, (Bu)4N+OHxe2x88x92, DBU and basic ion-exchange resins, particularly preferably NaOH and KOH.
Examples of a solvent capable of dissolving at least part of a base used include circular urea derivatives such as 1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidinone, 1,3-dipropyl-2-imidazolidinone and 1,3-dibutyl-2-imidazolidinone; amides such as formamide, N-methylformamide, N,N-dimethylformamide, N-methylacetamide, N,N-dimethylacetamide and hexamethylphosphoramide; dimethylsulfoxide; sulfolane; pyridine; morpholine; ethers such as tetrahydrofuran and 1,4-dioxane; nitrites such as acetonitrile and propionitrile; and lower alcohols such as methanol, ethanol and isopropanol. These solvents may be mixed with water or used in combination of two or more for improving a solubility of a base. When using a catalyst capable of solubilizing a base, any solvent which is inert to the reaction may be used. An example of a preferable solvent is a mixture of 1,3-dimethyl-2-imidazolidinone and water.
An example of a catalyst capable of solubilizing a base is a phase transfer catalyst. Examples of a phase transfer catalyst include cetyltrimethylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium bromide and tetrabutylammonium hydroxide.
When reacting the compounds represented by formulas (1) and (2) as the starting materials in the presence of a base in the first step of the process according to the present invention, a molar ratio of the starting materials is preferably base/ortho-alkylnitrobenzene derivative/acrylonitrile derivative=0.01 to 1.0/1/0.1 to 5 for preparation of a nitrobenzenenitrile derivative represented by formula (2) where X is nitrile; and base/ortho-alkylnitrobenzene derivative/acrylate=0.01 to 1.0/1/0.1 to 10 for preparation of a nitrobenzenecarboxylate represented by formula (2) where X is CO2R8.
When reacting the compounds represented by formulas (1) and (2) as the starting materials in the presence of a base in the first step of the process according to the present invention, the amount of a solvent capable of dissolving at least part of a base is 0.1 to 20 weight parts, preferably 0.5 to 20 weight parts to one part of an ortho-alkylnitrobenzene derivative, and the amount of a catalyst capable of solubilizing a base is 0.1 to 10 mole % to the ortho-alkylnitrobenzene derivative.
When reacting the compounds represented by formulas (1) and (2) as the starting materials in the presence of a base in the first step of the process according to the present invention, a reaction temperature may vary depending on a base and a solvent used, but is preferably 150xc2x0 C. or lower because the reaction must be conducted at a temperature equal to or lower than a decomposition temperature of an ortho-alkylnitrobenzene derivative. A reaction period may be generally 1 min to 6 hours.
When reacting the compounds represented by formulas (1) and (2) as the starting materials in the presence of a base in the first step of the process according to the present invention, a reaction pressure may be an ambient, increased or reduced pressure as long as the starting materials or the solvent may not be removed from the system, and may be generally an ambient pressure.
The reaction is preferably conducted in an atmosphere of an inert gas such as nitrogen or under oxygen-free conditions.
When an acrylate represented by formula (2) where X is CO2R8 is used as a starting material and a solvent is mixed with water, a reaction product contains a nitrobenzenecarboxylic acid derivative.
The reaction may be conducted batchwise or in a continuous system. The reaction may be quenched by pouring the reaction mixture into ice-water, and then the mixture is neutralized to pH 6 to 7 with an acid. After separating phases using an organic solvent, the organic solvent may be removed to provide a viscous liquid containing the desired aromatic nitro compound represented by formula (3).
Examples of an extraction solvent used include isopropyl ether, ethyl acetate, butyl acetate, carbon disulfide, carbon tetrachloride, hexane, cyclohexane, petroleum ether, toluene, xylenes, chloroform, dichloromethane, 1,2-dichloroethane, trichloroethylene, 1,2-dichlorobenzene, chlorobenzene, benzonitrile, nitromethane, nitrobenzene, anisole and diethyleneglycol dimethyl ether. Any solvent other than those described above may be used as long as it can dissolve the desired compound, can be separated from water, is stable under the phase separation process and has physical properties such as a boiling point within a preferable range.
Column chromatography or distillation at a reduced pressure of the viscous liquid thus obtained may provide a pure nitrobenzenenitrile derivative, nitrobenzenecarboxylic acid, nitrobenzenecarboxylate or nitrobenzenecarboxamide. When a mixture of a nitrobenzenecarboxylic acid and a nitrobenzenecarboxylate is obtained, each compound may be separately collected by column chromatography or distillation, or alternatively the mixture may be esterified or hydrolyzed to convert the carboxylic acid into the ester or the ester into the carboxylic acid before the collection.
These compounds may be collected and purified by recrystallization or column chromatography when they have a high melting point or are easily crystallized, or by distillation at a reduced pressure or column chromatography when they have a low melting point or are poorly crystallized and exhibit good thermal stability.
Examples of an aromatic nitro compound represented by formula (3) include 4-(2-nitrobenzene)butanonitrile, 4-(2-nitrobenzene)-2-methylbutanonitrile, 4-(2-nitrobenzene)-3-methylbutanonitrile, 4-(2-nitrobenzene)-3-ethylbutanonitrile, 4-(2-nitrobenzene)-3-chlorobutanonitrile, 4-(2-nitro-3-isopropylbenzene)butanonitrile, 4-(2-nitro-3-butylbenzene)butanonitrile, 4-(2-nitro-4-t-butylbenzene)butanonitrile, 4-(2-nitro-5-methylbenzene)butanonitrile, 4-(2-nitro-3-methylbenzene)-2-methylbutanonitrile, 4-(2-nitro-5-isopropylbenzene)butanonitrile, 4-(2-nitro-5-chlorobenzene)butanonitrile, 4-(2-nitrobenzene)butyric acid, 4-(2-nitrobenzene)-2-methylbutyric acid, 4-(2-nitrobenzene)-3-methylbutyric acid, 4-(2-nitrobenzene)-3-ethylbutyric acid, 4-(2-nitro-5-isopropylbenzene)butyric acid, 4-(2-nitro-5-chlorobenzene)butyric acid, 4-(2-nitrobenzene)-3-chlorobutyric acid, 4-(2-nitro-3-isopropylbenzene)butyric acid, 4-(2-nitro-3-butylbenzene)butyric acid, 4-(2-nitro-4-t-butylbenzene)butyric acid, 4-(2-nitro-5-methylbenzene)butyric acid, 4-(2-nitro-3-methylbenzene)-2-methylbutyric acid, methyl 4-(2-nitrobenzene)butyrate, methyl 4-(2-nitrobenzene)-2-methylbutyrate, methyl 4-(2-nitrobenzene)-3-methylbutyrate, methyl 4-(2-nitrobenzene)-3-ethylbutyrate, methyl 4-(2-nitrobenzene)-3-chlorobutyrate, methyl 4-(2-nitro-3-isopropylbenzene)butyrate, methyl 4-(2-nitro-3-butylbenzene)butyrate, methyl 4-(2-nitro-4-t-butylbenzene)butyrate, methyl 4-(2-nitro-5-methylbenzene)butyrate, methyl 4-(2-nitro-3-methylbenzene)-2-methylbutyrate, methyl 4-(2-nitro-5-isopropylbenzene)butyrate, methyl 4-(2-nitro-5-chlorobenzene)butyrate, ethyl 4-(2-nitrobenzene)butyrate, ethyl 4-(2-nitrobenzene)-2-methylbutyrate, ethyl 4-(2-nitrobenzene)-3-methylbutyrate, ethyl 4-(2-nitrobenzene)-3-ethylbutyrate, ethyl 4-(2-nitrobenzene)-3-chlorobutyrate, ethyl 4-(2-nitrobenzene)butyrate, ethyl 4-(2-nitro-3-isopropylbenzene)butyrate, ethyl 4-(2-nitro-3-butylbenzene)butyrate, ethyl 4-(2-nitro-4-t-butylbenzene)butyrate, ethyl 4-(2-nitro-5-methylbenzene)butyrate, ethyl 4-(2-nitro-3-methylbenzene)-2-methylbutyrate, ethyl 4-(2-nitro-5-isopropylbenzene)butyrate, ethyl 4-(2-nitro-5-chlorobenzene)butyrate, cyclohexyl 4-(2-nitrobenzene)butyrate, phenyl 4-(2-nitrobenzene)butyrate, benzyl 4-(2-nitrobenzene)butyrate, 4-(2-nitrobenzene)butyramide, 4-(2-nitrobenzene)-2-methylbutyramide, 4-(2-nitrobenzene)-3-methylbutyramide, 4-(2-nitrobenzene)-3-ethylbutyramide, 4-(2-nitro-5-isopropylbenzene)butyramide, 4-(2-nitro-5-chlorobenzene)butyramide, 4-(2-nitrobenzene)-3-chlorobutyramide, 4-(2-nitro-3-isopropylbenzene)butyramide, 4-(2-nitro-3-butylbenzene)butyramide, 4-(2-nitro-4-t-butylbenzene)butyramide, 4-(2-nitro-5-methylbenzene)butyramide and 4-(2-nitro-3-methylbenzene)-2-methylbutyramide. In particular, 4-(2-nitrobenzene)butanonitrile, 4-(2-nitrobenzene)butyric acid, methyl 4-(2-nitrobenzene)butyrate, ethyl 4-(2-nitrobenzene)butyrate and 4-(2-nitrobenzene)butyramide are preferable because they may be readily converted into a 5-nitro-1-tetralone which is used in a variety of applications.
There will be described the cyclization in the second step in the process according to the present invention.
The cyclization of an aromatic nitro compound represented by formula (3) into a 5-nitro-1-tetralone derivative represented by formula (4) is usually conducted using an acid catalyst. Examples of such an acid include strong acids such as sulfuric acid and polyphosphoric acid; superacids such as oleum, chlorosulfonic acid, trifluoromethanesulfonic acid and fluorosulfonic acid; and Lewis-acid-containing superacids such as fluorosulfonic acid or chlorosulfonic acid containing a small amount of, e. g., SO3 or SbF5. Solid superacids such as sulfated zirconia and sulfated tin oxide may be also used. The amount of the acid is one or more equivalent to the substrate represented by formula (3). The cyclization may be conducted in such an acid or in a solvent inert to the acid.
A reaction temperature is generally 20xc2x0 C. to 200xc2x0 C., preferably 50 to 150xc2x0 C. A reaction period is generally 5 min to 15 hours, preferably 20 min to 10 hours.
A reaction pressure may be an ambient or increased pressure or, if the appropriate reaction temperature can be maintained, a reduced pressure.
The reaction may be conducted batchwise or in a continuous system.
Water is added to a reaction mixture. Phases are separated using an organic solvent. After washing the organic layer with water, the organic solvent is removed to give a crude 5-nitro-1-tetralone derivative. The acid may be recovered by distillation before adding water. The recovered acid by distillation may be reused in the cyclization. When an excessive superacid is used, the superacid is preferably removed from the reaction mixture by, for example, distillation before adding water. Since addition of water to a strong acid may be an exothermic process, water is preferably added with cooling. The acid used is diluted or decomposed with water or methanol generated together with a tetralone derivative from the cyclization (hereinafter, such a diluted or decomposed acid is referred to as a xe2x80x9cwaste acidxe2x80x9d). For example, when using fluorosulfonic acid in the reaction, it is decomposed with water or methanol to form HF, sulfuric acid and so on. The waste acid thus generated may be used to neutralize a base used in the reaction between the compounds represented by formulas (1) and (2).
Examples of an organic solvent used herein include isopropyl ether, ethyl acetate, butyl acetate, carbon disulfide, carbon tetrachloride, hexane, cyclohexane, petroleum ether, toluene, xylenes, chloroform, dichloromethane, 1,2-dichloroethane, trichloroethylene, o-dichlorobenzene, chlorobenzene, benzonitrile, nitromethane, nitrobenzene, anisole and diethyleneglycol dimethyl ether, particularly preferably isopropyl ether, ethyl acetate and butyl acetate. Any solvent other than those described above may be used as long as it can dissolve the desired compound, can be separated from water, is stable under the phase separation process and has physical properties such as a boiling point within a preferable range.
When an aromatic nitro compound represented by formula (3) is a nitrobenzenecarboxamide, the cyclization for forming a 5-nitro-1-tetralone derivative represented by formula (4) may be conducted by contacting the material with a dehydrating agent. The dehydrating agent may be preferably acidic; for example, polyphosphoric acid and phosphorous oxides. These dehydrating agents may be used alone or in combination with the strong acid described above. A reaction temperature and a reaction period may vary depending on the types of the acid and the dehydrating agent, but it must be 200xc2x0 C. or lower because an excessively elevated temperature may cause decomposition of a reaction product. A reaction pressure may be an ambient, increased or reduced pressure as long as an appropriate reaction temperature may be maintained. A reaction solvent, if used, is preferably inert in the reaction and contains a minimum amount of water. The reaction is preferably conducted in a liquid phase and may be conducted batchwise or in a continuous system.
The crude 5-nitro-1-tetralone derivative may be purified by recrystallization when it has a high melting point or is readily crystallized, or by distillation when it has a low melting point or is less crystallizable.
Examples of a 5-nitro-1-tetralone derivative represented by formula (4) include 5-nitro-1-tetralone, 5-nitro-2-methyl-1-tetralone, 5-nitro-3-methyl-1-tetralone, 5-nitro-3-ethyl-1-tetralone, 5-nitro-3-chloro-1-tetralone, 5-nitro-4-n-propyl-1-tetralone, 5-nitro-6-isopropyl-1-tetralone, 5-nitro-6-n-butyl-1-tetralone, 5-nitro-7-t-butyl-1-tetralone, 5-nitro-8-methyl-1-tetralone, 5-nitro-8-chloro-1-tetralone, 5-nitro-2,6-dimethyl-1-tetralone, 5-nitro-4,8-dimethyl-1-tetralone and 5-nitro-8-isopropyl-1-tetralone. In particular, 5-nitro-1-tetralone is preferable because it may be converted into 1,5-diaminonaphthalene.
There will be described a conversion into a 1,5-diaminonaphthalene derivative in the third step in the process according to this invention.
A 5-nitro-1-tetralone derivative represented by formula (4) may be then converted into a desired 1,5-diaminonaphthalene derivative by 1) oxime formation, conversion into a 5-nitro-1-aminonaphthalene derivative, and then reduction of the nitro groups, or 2) imine formation, aromatization and then reduction of the nitro groups.
A 5-nitro-1-tetralone derivative may be converted into an oxime by a common oxime-formation process. An oxime-forming agent may be hydroxylamine or a salt of hydroxylamine. Examples of a salt of hydroxylamine include hydroxylamine hydrochloride and hydroxylamine sulfate. Hydroxylamine may be obtained by neutralizing such a salt with a basic compound or by reacting ammonia with a peroxide such as hydrogen peroxide. Hydroxylamine may be isolated by an appropriate method such as distillation, and may be used after extraction, or directly used as it is.
A reaction solvent in the oxime formation may be any solvent which is inert in the reaction. Examples of such a solvent include alcohols and alcohols containing an acidic compound such as acetic acid.
A reaction temperature is from 20xc2x0 C. to a temperature at which hydroxylamine or its salt decomposes. It is generally 20 to 150xc2x0 C., preferably 50 to 120xc2x0 C.
A reaction pressure may be an ambient pressure, but an increased or reduced pressure may be employed as long as an appropriate reaction temperature may be maintained.
A reaction period is 1 min or longer. A product may be isolated by an appropriate method such as distillation, recrystallization, reprecipitation and column chromatography, or some of the reaction solvent may be evaporated. Alternatively, when the reaction solvent is inert in the next step, the reaction mixture may be directly used without further concentration or isolation.
Conversion of the oxime into a 5-nitro-1-aminonaphthalene derivative may be conducted using a reagent capable of cleaving the Nxe2x80x94O bond in the oxime group (xe2x95x90NOH) in a dehydration reaction. For example, the oxime may be heated in acetic acid as a solvent in the presence of hydrochloric acid to provide a desired 5-nitro-1-aminonaphthalene hydrochloride. A reaction temperature and a reaction period may vary depending on a reagent used, and may be chosen such that the Nxe2x80x94O bond in the oxime group can be cleaved in a dehydration reaction as described above. A reaction temperature is generally 50 to 250xc2x0 C., preferably 50 to 200xc2x0 C. For facilitating elimination of OH, the OH in the oxime group may be converted into a functional group which may be readily eliminated, for example, into OCOCH3 using acetic anhydride. A reaction pressure may be an ambient or increased pressure. When the dehydrating reagent is gaseous, it may be fed at an ambient pressure, but it is advantageously charged in a closed system at an increased pressure.
After the oxime formation, conversion into a 5-nitro-1-aminonaphthalene derivative is conducted, which may be a one-step reaction.
The nitro group may be converted into an amino group by directly using a method for converting a nitrobenzene derivative into an aniline derivative, but reduction with hydrogen using a hydrogenation catalyst is the most cost-effective process. Examples of a hydrogenation catalyst include Raney metals such as Raney Ni and Raney Co; and platinum-group catalysts such as Pd/C and Pt/alumina. The reaction may be conducted in a gaseous or liquid phase. A solvent used in a liquid phase reaction may be any inert solvent in the reaction, preferably alcohols and amides. A reaction temperature is generally an ambient temperature to 150xc2x0 C., preferably 50 to 100xc2x0 C. A reaction pressure may be an ambient pressure or higher, but an excessively higher hydrogen pressure may cause hydrogenation on the naphthalene ring.
All the reactions of oxime formation, conversion into an aminonaphthalene derivative and reduction of a nitro group may be conducted batchwise or in a continuous system.
Alternatively, a 5-nitro-1-tetralone derivative may be converted into a 1,5-diaminonaphthalene derivative via an imine instead of an oxime.
A 5-nitro-1-tetralone derivative may be converted into an imine by reacting the nitro compound with an excessive amount of ammonia and/or an ammonium salt. In the reaction, a dehydrating agent may be added. The reaction may be conducted at an ambient or increased pressure, but when using ammonia, the reaction is preferably conducted at an increased pressure.
Aromatization of the tetralin ring and reduction of the nitro groups after imine formation may proceed via hydrogen transfer, using a hydrogenation catalyst such as Raney metals, e. g., Raney Ni and Raney Co and platinum group catalysts, e. g., Pd/C and Pt/alumina. Hydrogenation may be conducted in the presence of hydrogen for reducing partially remaining nitro and nitroso groups. Aromatization of the tetralin ring and reduction of the nitro group may be conducted in one step. Specifically, the imine may be converted into a 1,5-diaminonaphthalene derivative using a hydrogenation catalyst in the presence of hydrogen.
Alternatively, a 5-nitro-1-tetralone derivative may be converted into a 1,5-diaminonaphthalene derivative using a hydrogenation catalyst in the presence of ammonia and/or an ammonium salt together with hydrogen.
All the reactions of imine formation, aromatization and reduction of the nitro group may be conducted in a gaseous or liquid phase, and batchwise or in a continuous system.
A product 1,5-diaminonaphthalene derivative in the present invention is a compound represented by general formula (5), where R1 to R4 and R6 to R7 are as defined in formulas (1) and (2).
Examples of a 1,5-diaminonaphthalene derivative used in the present invention include 1,5-diaminonaphthalene, 2-methyl-1,5-diaminonaphthalene, 3-methyl-1,5-diaminonaphthalene, 3-ethyl-1,5-diaminonaphthalene, 3-chloro-1,5-diaminonaphthalene, 4-n-propyl-1,5-diaminonaphthalene, 6-isopropyl-1,5-diaminonaphthalene, 6-n-butyl-1,5-diaminonaphthalene, 7-t-butyl-1,5-diaminonaphthalene, 8-methyl-1,5-diaminonaphthalene, 6-chloro-1,5-diaminonaphthalene, 2,6-dimethyl-1,5-diaminonaphthalene and 4,8-dimethyl-1,5-diaminonaphthalene.
This invention will be further described with reference to, but not limited to, Examples.